METAL’S role in traditional construction has ancient origins. The extraction and use of lead in Britain dates at least to the Roman period. Handmade iron nails have been produced for 2,000 years or more and any historic handmade nail used in a British building is likely to date from before 1800. Metal was not always essential to the construction of traditional structures – wooden pegs rather than nails, for example, could be used for carpentry joints and to hold tiles in place – but it often assisted or simplified the building process. Its disadvantages included the considerable costs involved in extraction and production and the possibility of corrosion. Fuel needs for manufacture were substantial and led the Scottish Parliament to control charcoal production in 1609 after witnessing dramatic deforestation in England, due in part to the iron industry. However, by the late nineteenth century, with easier transportation and cheaper production, it was possible for a new material like corrugated iron roof sheeting to supersede thatch. It offered an inexpensive and simply fixed alternative that required little maintenance.
The earliest iron-framed building in the world dates from the late eighteenth century: the flax mill at Ditherington, Shropshire. Metal framing was developed for industrial buildings where it allowed exceptionally wide roof spans and assisted with fireproofing. Iron construction quickly found other non-domestic uses, including the impressive, cast-iron dome of the Perth Waterworks of 1832, made by the Dundee Iron Foundry. By the mid-late nineteenth century iron frontages, combined with newly available plate glass, began to be introduced to commercial premises. Good examples include the showroom now used by Arighi Bianchi in Macclesfield, with a front of 1883. Evidence for use of iron in a lesser role, but still as a primary structural element, can be found even earlier. Gunn’s Mill in the Forest of Dean, which was once a blast furnace, has iron lintels cast with the date 1682/3. Metal also played an important role in many traditionally built houses, though its use was generally confined to a range of coverings and fixings.
Artist George Robertson’s sketch of an iron foundry at Coalbrokedale, Shropshire, in the 1780s. Note the crane in the centre and, to the left, the ladle used for pouring molten metal.
Metals in building can be immensely durable, but are not immune to decay. Even lead, which can survive well over a hundred years as roofing sheets, can suffer rapid underside corrosion if not laid well. At least when decay makes replacement essential, metals have the advantage of eminent recyclability. A Nottinghamshire plumber’s bill from 1765 shows how the total of £27 19s 1¼ d was reduced by around £3 when old lead was taken into account, at a rate of 14s per cwt [50 kilograms]. In the same year a Warwickshire deed recorded how lead pipes and guttering and an old tank were ‘all since cast into the new Cisterne of leade … and into two new gutters of lead there now made.’
An early twentieth century blacksmith’s shop at Weymouth, Dorset. In the window advertising cards read: ‘Made to order of JA Parsons & Son Builder, Weymouth’ and ‘from a set of hinges made for Salisbury Cathedral’.
Corrugated iron was first patented in the 1820s. With its earthy rust-red colour it has become a traditional roofing material in many rural areas. This cottage is on the Isle of Man.
Iron used in building could be cast or wrought. Both were derived from iron-rich stone. This ore was heated in a furnace until the molten material was ready to be cast into ingots called ‘pigs’. Wrought or puddled iron was worked at intervals to drive out impurities, producing a fibrous grain and useful ductility. It had a considerable range of uses in the smith’s hands, some of which related to building. Smeaton, in his Builder’s Pocket Manual of 1837, praised wrought iron for use in construction but commented that, ‘on account of it being more expensive than cast iron, it is seldom used for heavy work.’ He added that, due to its tensile strength, ‘iron ties and other small pieces [of metal] used in construction are [best if] formed from wrought iron.’ From the 1850s, with developments in manufacturing methods, mild steel became wrought iron’s successor.
Iron being used to strengthen the junction between stones in a parapet. Iron that corrodes and expands can cause serious damage to stonework.
Cast iron, in comparison, is relatively brittle, but its fibrous crystalline structure copes well with compression. It has been used in Europe since the fifteenth century. In traditionally built British houses it is most commonly found in non-structural elements such as fire grates, balustrades or guttering, but has had some structural uses, particularly since the nineteenth century. These have included columns, balconies and conservatories. Foundries cast iron by heating it so that it could be poured into moulds formed in sand by an impressed timber pattern. In more advanced casting, a two-sided mould would be used with the halves joined before the molten material was poured in.
Inside a working blacksmith’s forge in Surrey, owned by the Society for the Protection of Ancient Buildings.
As this Scottish cottage shows, corrguated iron could provide a material for wall coverings as well as roof sheeting.
Iron was also used for fixings in stonework, providing strengthening where a mortar joint would be insufficiently robust. In the long term, however, this could have disastrous effects on the stone; rusting caused expansion, leading to localised stone damage. Iron nails were also used in their millions in traditional buildings. Hand-forged nails began to be superseded by cut nails in the sixteenth century, but from the nineteenth century machine-cut, stamped and wire nails were introduced, with galvanisation to protect against rust from around 1840.
A selection of iron nails and fixings as illustrated in Mitchell’s Building Construction, 1909.
Cast iron has had many non-structural uses on the exteriors of traditional buildings. Gutters and downpipes could be made decorative as well as functional.
On this early eighteenth-century carved stone porch in Corsham, Wiltshire lead sheet was used for added weather protection.
The word ‘plumbing’ derives from the Latin for lead but, without irony, pipework for water is often now claimed to be ‘lead free’. Despite this, lead has continued to be used for many building purposes, where its potential toxicity is considered less problematic and its malleability and durability have great advantages. Traditionally, it was formed into gutters, downpipes and hopper heads for the disposal of rainwater. In sheet form lead could be used to cover roofs, to provide cappings for architectural features such as pediments and porches, or as flashings and soakers to form weathertight junctions between other materials.
Lead is produced from lead sulphide (or galena), an ore found at various British sites including Wanlockhead in Scotland. In 1810 Pennant noted in his Tours in Wales how one ancient mining site in Flintshire was called ‘Pentre Ffwrndan, or place of the fiery furnace; a name it was always known by and which evinces the antiquity of smelting in these parts.’ The Yatestoop mine near Winster in Derbyshire was described in the eighteenth century as ‘a cavity (often near horizontal) between the beds of limestone having a narrow rake vein (that is a straight vertical leading from it to the surface) … it contains much lead.’ Lead was always a valuable commodity. In the Manor of Shelve, Shropshire, in the mid seventeenth century, ‘ancient lead-mines in the wastes’ were re-opened and proved ‘rich’. The Lord of the Manor, seeing this new source of wealth was later claimed to have ‘caused his servants to enter upon the said mine ... and to seise the lead ... And has ever since continued the possession by force and gets lead there which he disposes at his pleasure.’
An expert leadworker from CEL Leadwork manufacturing a hopper head for a rainwater system. The lead is shaped and finished around a wooden former.
Lead sheet for construction has been produced in two ways. Since the later seventeenth century, milled or rolled lead has been available. Milling allows production of thin sheets. The older – but some would say superior – production method is casting. This process, which is now restricted to a small number of specialist leadworks but once occurred on building sites, involves pouring and levelling molten lead on a large, flat bed of sand. Cast lead is usually distinguishable by the slight pitting of its surface, caused by the sand, and is often produced in thicker sheets than the milled alternative. Smeaton explained in 1817 that ‘All lead is valued according to its thickness, that is to say, according to the number of pounds contained in every square foot.’ He also described how this could be the basis for deception, since subtle differences in lead thickness were difficult to spot ‘the plumber often deceives the architect, [by using] … a lead of less weight than is contracted for [since it] requires considerable practice in order to detect, by the feel, whether the lead is as heavy as was required.’ Lead is now categorised by ‘codes’, with a thin milled sheet perhaps being ‘code 4’, but sand-cast lead often ‘code 10’ or more – that is 10 pounds per square foot.
Sand-casting of sheet lead at the workshop of Norman and Underwood, Leicester. Note the hand prints in the sand bed, which have been transferred to the lead.
Lead laid in steps to form a parapet gutter. The steps allow a fall so that rainwater flows away and for the sheets to be of a length that avoids splitting under thermal expansion and contraction.
When lead sheets were used on roofs and for gutters, particular care was needed with both the slope and the jointing. Lead could work successfully at much flatter pitches than slate or tiles, but still required a slight fall to shed water. It also had to be jointed in a way that accommodated the significant expansion and contraction caused by temperature change. In 1695, during the construction of one of Christopher Wren’s buildings, the plumber was instructed to ‘cast his sheets even and to lay them loose, that when the Sunn is hott on them the sheets may have liberty to give way and not crack.’ Lead sheets are generally laid onto timber boards. Where the sheets overlap the joints are raised and formed around timber cores of circular section, or sometimes as hollow rolls.
A selection of traditional leadworking tools made from close-grained box wood.
Lead was also useful for weather protection at the junction between building surfaces, such as a chimneystack and a roof. The malleable metal would be dressed into mortar joints in the masonry and beaten into shape to bridge the gap. The leadworker would use a range of tools, traditionally made from a strong, tightly grained timber such as box wood. For repairs to damaged leadwork, or to form specialist details such as sumps to gutters, the metal could be joined using a solder of tin and lead. In the twentieth century, lead-burning using oxyacetylene was introduced as an alternative.
The softness of lead has encouraged a long tradition of graffiti. Outlines of feet are common, as are dates and initials. Occasionally obscenities are also found!
Other metals, such as zinc, aluminium and terne-coated steel were marketed as alternatives to lead during the twentieth century. An older rival was copper. In Britain it never enjoyed lead’s popularity, but has some advantages in being lighter and slightly less prone to expansion and contraction. Richard Carew noted, in 1602, how copper was found in ‘sundrie places’ in Cornwall, but was shipped to be refined in Wales, ‘either to save cost in the fewell or to conceale the profit.’ Copper can be used for flashings and gutters. It can also serve as a covering for whole roofs, and was particularly popular for lightweight structures such as the balconies of Regency villas. Junctions between sheets can be formed either with standing seams or with wooden cores though, in contrast to leadwork, these are traditionally conical rather than circular in section. On weathering, leadwork forms a whitish bloom, whereas copper assumes a distinctive green verdigris (copper carbonate).
Mynnyd Parys, north Anglesey, has been mined for copper for thousands of years. In the eighteenth century it became Europe’s largest copper mine, competing with sites in Cornwall.
Copper sheeting, with its distinctive verdigris colour, seen here on the roof of an early nineteenth-century first floor verandah.
Copper slag blocks, like these in Bristol, were a by-product of the metal industry. They are also to be found in Cornwall and Gloucestershire, mostly dating from the eighteenth century.
Metals have crossed the divide between traditional and modern forms of construction. In ancient times use was restricted to the houses of the wealthy, but their supply and affordability gradually increased so that by the start of the twentieth century they formed a part of most domestic structures. As in all cases where a building material has become traditional, a combination of reasonable cost, local availability and practical value led to an enduring pattern of use.
Copper slag could also be employed as a component of external render as seen on the lower wall of this Georgian house in Bristol.
